U.S. patent application number 13/473825 was filed with the patent office on 2012-09-06 for ink jet print head.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Akiko Saito, Ken Tsuchii.
Application Number | 20120224006 13/473825 |
Document ID | / |
Family ID | 42540081 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120224006 |
Kind Code |
A1 |
Saito; Akiko ; et
al. |
September 6, 2012 |
INK JET PRINT HEAD
Abstract
An ink jet print head is provided which has a reduced size and
still can prevent an overall temperature increase in a printing
element board. To this end, among ink supply port arrays formed on
both sides of each nozzle array, the heat resistance of the portion
(beams) of the printing element board between the adjoining ink
supply ports is lowered in those arrays that are close to the end
portions of the common liquid chamber.
Inventors: |
Saito; Akiko; (Tokyo,
JP) ; Tsuchii; Ken; (Sagamihara-shi, JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
42540081 |
Appl. No.: |
13/473825 |
Filed: |
May 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12691160 |
Jan 21, 2010 |
8201925 |
|
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13473825 |
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Current U.S.
Class: |
347/62 |
Current CPC
Class: |
B41J 2/14145 20130101;
B41J 2002/14467 20130101; B41J 2/1404 20130101 |
Class at
Publication: |
347/62 |
International
Class: |
B41J 2/05 20060101
B41J002/05 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2009 |
JP |
2009-026170 |
Claims
1-7. (canceled)
8. A liquid ejection head comprising: a plurality of arrays of
elements which are formed on one side of a board, which generate
energy that is used to eject a liquid, and which are arranged in a
first direction; a plurality of arrays of ejection openings for
ejecting liquid which are arranged such that the ejection openings
correspond to a plurality of the elements; and a plurality of
arrays of supply ports for supplying the liquid to the elements
which pierce through the one side and another side of the board and
which are arranged in the first direction, wherein the plurality of
arrays of supply ports and the plurality of arrays of elements are
alternately arranged in a second direction which intersects with
the first direction, the plurality of arrays of supply ports
include a first array of supply ports arranged at a side of an end
of the board in the second direction and a second array of supply
ports arranged at a center of the board in the second direction, an
interval between the supply ports included in the first array of
supply ports is longer than an interval between the supply ports
included in the second array of supply ports.
9. The liquid ejection head according to claim 8, wherein a supply
port included in the first array of supply ports is rectangular in
shape with its longer dimension being in the second direction, and
a supply port included in the second array of supply ports is
rectangular in shape with its longer dimension being in the first
direction.
10. The liquid ejection head according to claim 8, wherein a common
liquid chamber connected to the first array of supply ports and the
second array of supply ports is formed on the other side of the
board.
11. The liquid ejection head according to claim 8, wherein flow
path walls are formed between elements of the plurality of arrays
of elements.
12. The liquid ejection head according to claim 8, wherein one of
the plurality of element arrays is formed near the side of the end
of the board adjacent the first array of supply ports.
13. The liquid ejection head according to claim 8, wherein a
thickness of the board at a region where the plurality of supply
ports is formed is substantially uniform.
14. A liquid ejection head comprising: a plurality of arrays of
elements which are formed on one side of a board, which generate
energy that is used to eject a liquid, and which are arranged in a
first direction; a plurality of arrays of ejection openings for
ejecting liquid which are arranged such that the ejection openings
correspond to a plurality of the elements; and a plurality of
arrays of supply ports for supplying the liquid to the elements
which pierce through the one side and another side of the board and
which are arranged in the first direction, wherein the plurality of
arrays of supply ports and the plurality of arrays of elements are
alternately arranged in a second direction which intersects with
the first direction, the plurality of arrays of supply ports
include a first array of supply ports arranged at a side of an end
of the board in the second direction and a second array of supply
ports arranged at a center of the board in the second direction,
and an area of the board between two adjacent supply ports in the
first array of supply ports is greater than an area of the board
between two adjacent supply ports in the second array of supply
ports.
15. The liquid ejection head according to claim 14, wherein a
supply port included in the first array of supply ports is
rectangular in shape with its longer dimension being in the second
direction, and a supply port included in the second array of supply
ports is rectangular in shape with its longer dimension being in
the first direction.
16. The liquid ejection head according to claim 14, wherein a
common liquid chamber connected to the first array of supply ports
and the second array of supply ports is formed on the other side of
the board.
17. The liquid ejection head according to claim 14, wherein a
thickness of the board at a region where the plurality of supply
ports is formed is substantially uniform.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an ink jet print head that
ejects ink onto a print medium to perform printing.
[0003] 2. Description of the Related Art
[0004] Ink jet printing systems are in wide use today not only due
to their ability to print highly defined images at high speeds, but
also due to their ability to perform printing on even a print
medium not subjected to special treatments. Ink jet print heads
that actualize these ink jet printing systems have various types of
ejection systems, which are typified by the use of the energy of
heat-generated bubbles to eject ink, or the use of piezoelectric
elements.
[0005] In recent years, with respect to such ink jet print heads,
there has been a growing demand for higher print quality and faster
printing speed. Means that have been proposed to increase the
printing speed include increasing the number of nozzles in the ink
jet print head and improving the ejection frequency.
[0006] One of the factors that determines the upper limit of the
ejection frequency of an ink jet print head is the time it takes
for a nozzle, after ejecting ink, to be supplied and filled with
ink again (also referred to as refill time). The shorter this
refill time becomes, the higher the ejection frequency will be at
which the printing can be performed.
[0007] FIG. 11 is a partially cut-away cross section view showing
the interior of a conventional print head. In a conventional nozzle
structure, which supplies ink from a single ink supply port 95
opening along arrays of nozzles through only one ink path 97 into
pressure chambers 96, the refill time is dictated by the flow
resistance of the ink flow path. As a means to reduce the refill
time, Japanese Patent Laid-Open No. H10-181021(1998) discloses a
technique that arranges flow path walls so as to form a plurality
of flow paths in each of the pressure chambers, thereby increasing
the number of ink inflow paths.
[0008] To obtain highly defined, deep-grayscale, high-quality
printed images, there are currently demands for an ink jet print
head which has low variation in the ejection volume of any
particular nozzle, and low variation among the different nozzles in
the print head. Regarding ink jet print heads that eject ink via
the force of an expanding bubble, however, the amount of ink
ejected changes with the temperature near the ejection opening.
Particularly when there is a local temperature distribution within
the nozzle array, the ink ejection volume varies according to the
temperature distribution, resulting in a printed image having
density variations and therefore a degraded image quality.
Although, to deal with this situation, a variety of measures have
been taken on the ink jet printing apparatus body side, such as
multi-path techniques and drive pulse control, the stabilization of
the ink ejection volume depends largely on the stand alone
performance of the ink jet print head.
[0009] Japanese Patent Laid-Open No. H10-157116(1998) discloses a
technique to reduce printing variations that makes the temperature
near the end of the print head and the temperature near the central
portion thereof almost equal by the provision of heat dissipating
fins at the center of the print head.
[0010] To minimize image quality degradations caused by an increase
in temperature distribution of an ink jet print head, Japanese
Patent Laid-Open No. 2003-170597 discloses a technique that
introduces a heat conductive film into a print head board and
connects it to a heat dissipating portion that dissipates heat to
the ink, thereby suppressing the overall temperature rise. Japanese
Patent Laid-Open No. 2003-118124 discloses a technique that cools
the print head board itself via an ink flow supplied to the print
head.
[0011] The conventional ink jet print head has a single ink supply
port opening along the nozzle arrays, as shown in FIG. 11. In this
configuration, pressure generated in the pressure chamber 96 by an
expanding bubble escapes toward the ink path 97, with the result
that the generated pressure may not be fully utilized for ink
ejection. Since the pressure escapes toward the ink path 97, the
ejected ink may stray from the intended direction.
[0012] Further, in the conventional configuration, heat generated
by a heating resistor is transmitted through the print head board
and dissipated outside the nozzle arrays. This is because the
portion where the ink supply port is provided constitutes a heat
insulating portion, allowing the heat generated by the heating
resistor only to escape toward the outside of the nozzle arrays.
This configuration makes it difficult for heat to escape. A local
temperature rise in the print head board may be reduced by widening
the interval between the heating resistors to increase the heat
escape path. In that case, the print head board becomes large in
size.
SUMMARY OF THE INVENTION
[0013] It is therefore an object of the invention to provide an ink
jet print head that can reduce the size of the print head while
suppressing the overall temperature rise of the print head
board.
[0014] The ink jet print head of the present invention comprises a
common liquid chamber formed on a first surface of a print head
board, ink supply ports through which ink is supplied from the
common liquid chamber to nozzles, heating resistors installed on a
second surface, opposite the first surface, of the print head
board, a plurality of arrays of the nozzles capable of ejecting ink
from their ejection openings by energizing the heating resistors,
and a plurality of arrays of the ink supply ports, wherein the
plurality of nozzle arrays include a first nozzle array situated on
an end portion side of the common liquid chamber and a second
nozzle array situated on a central side of the common liquid
chamber, wherein the plurality of ink supply port arrays include a
first ink supply port array formed along at least one nozzle array
and situated on an end portion side of the common liquid chamber
and a second ink supply port array situated on a central side of
the common liquid chamber, wherein either the first nozzle array or
the second nozzle array is situated between the first ink supply
port array and the second ink supply port array, and wherein a heat
resistance of a portion of the print head board situated between
the adjoining ink supply ports in the first ink supply port array
is smaller than a heat resistance of a portion of the print head
board situated between the adjoining ink supply ports in the second
ink supply port array.
[0015] According to the invention, a plurality of nozzle arrays
include a first nozzle array situated on an end portion side of a
common liquid chamber and a second nozzle array situated on a
central side of the common liquid chamber. As for ink supply ports,
a first ink supply port array formed along a nozzle array and
situated on an end portion side of the common liquid chamber and a
second ink supply port array situated on a central side of the
common liquid chamber are included. Either the first nozzle array
or the second nozzle array is situated between the first ink supply
port array and the second ink supply port array. The portion of the
print head board situated between adjoining ink supply ports in the
first ink supply port array has a smaller heat resistance than the
portion of the print head board situated between adjoining ink
supply ports in the second ink supply port array.
[0016] This arrangement has actualized an ink jet print head that
can have a reduced size yet still prevent the overall temperature
of the printing element board from rising.
[0017] Further features of the present invention will become
apparent from the following description of exemplary embodiments
(with reference to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an external view of a mechanical construction of
an ink jet printing apparatus of one embodiment of this
invention;
[0019] FIG. 2 is an external view of a head cartridge used in the
ink jet printing apparatus of the embodiment;
[0020] FIG. 3 is an external view of a print head;
[0021] FIG. 4 is a schematic view of nozzle array groups in a print
head of the first embodiment of this invention, with one part of a
printing element board shown enlarged;
[0022] FIG. 5 is a cross section taken along the line V-V' of FIG.
4;
[0023] FIG. 6 shows a comparative example with respect to the first
embodiment;
[0024] FIG. 7 shows an example of an alternative implementation of
the first embodiment;
[0025] FIG. 8 is a schematic view of nozzle array groups in a print
head of a second embodiment of this invention, with one part of a
printing element board shown enlarged;
[0026] FIG. 9 shows an example of an alternative implementation of
the second embodiment;
[0027] FIG. 10 is a schematic view of nozzle array groups in a
print head of a third embodiment of this invention, with one part
of a printing element board shown enlarged; and
[0028] FIG. 11 is a partly cut-away cross-sectional diagram showing
the interior of a conventional print head.
DESCRIPTION OF THE EMBODIMENTS
First Embodiment
[0029] Now, a first embodiment of the invention will be described
with reference to the accompanying drawings.
[0030] FIG. 1 shows an external view of the mechanical structure of
an ink jet printing apparatus of this embodiment, FIG. 2 shows an
external view of a head cartridge used in this ink jet printing
apparatus and FIG. 3 shows an external view of a print head of the
head cartridge. A chassis 10 of the ink jet printing apparatus in
this embodiment comprises a plurality of plate-like metal members
with a predetermined rigidity. The chassis 10 has a print medium
feed unit 11 to automatically feed a sheet of print medium (not
shown) into the interior of the ink jet printing apparatus. The
chassis 10 also has a medium transport unit 13 for moving the print
medium supplied from the print medium feed unit 11 to a desired
print position and further moving it from the print position to a
medium discharge unit 12, a print unit for executing a
predetermined print operation on the print medium at the print
position and a head recovery unit 14 for executing an ejection
performance recovery operation on the print unit.
[0031] The print unit comprises a carriage 16 supported such that
it can be moved along a carriage shaft 15 and a head cartridge 18
removably mounted in this carriage 16 through a head set lever
17.
[0032] The carriage 16 in which the head cartridge 18 is mounted is
provided with a carriage cover 20 that positions an ink jet print
head 19 (also referred to simply as a print head) at a
predetermined mounting position on the carriage 16. The carriage 16
is also provided with the head set lever 17 that engages with a
tank holder 21 of the print head 19 to push and position the print
head 19 at the predetermined mounting position. The head set lever
17 for fixing and removing the print head is pivotally mounted on a
head set lever shaft (not shown) on the top of the carriage 16. The
carriage 16 also has at its engagement portion with the print head
19 a spring-biased head set plate (not shown), which by its spring
force presses the print head 19 against the carriage 16 for secure
mounting of the print head.
[0033] A contact flexible print cable (or simply referred to as a
contact FPC) 22 is connected at one end to the carriage 16 at
another engagement portion with the print head 19. When a contact
portion, not shown, formed at one end of the contact FPC 22 comes
into electrical contact with a contact portion 23 of the print head
19, which serves as an external signal input terminal, various
pieces of information for printing, and electricity are supplied to
the print head 19.
[0034] Between the contact portion of the contact FPC 22 and the
carriage 16 is installed an elastic member such as rubber, not
shown. The elastic force of the elastic member and the pressing
force of the head set plate combine to ensure a reliable connection
between the contact portion of the contact FPC 22 and the contact
portion 23 of the print head 19. The other end of the contact FPC
22 is connected to a carriage board, not shown, mounted at the back
of the carriage 16.
[0035] The head cartridge 18 of this embodiment has an ink tank 24
storing ink and the print head 19 that ejects ink supplied from the
ink tank 24 from the ejection openings of the print head 19
according to print information. The print head 19 of this
embodiment is of a so-called cartridge type that can be removably
mounted on the carriage 16.
[0036] For photographic high-quality color printing, this
embodiment allows the use of six independent ink tanks 24 for
black, light cyan, light magenta, cyan, magenta and yellow ink.
Each of the ink tanks 24 is provided with an elastically deformable
release lever 26 that locks onto the head cartridge 18. By
operating the associated release lever 26, individual ink tanks 24
can be removed from the print head 19, as shown in FIG. 3. The
release levers 26 therefore function as part of a
mounting/dismounting means of this invention. The print head 19
comprises a printing element board described later, an electric
wiring board 28 and the tank holder 21. The printing element board
is electrically connected to the electric wiring board 28 through
contacts at a square hole 25 in the electric wiring board 28.
[0037] FIG. 4 shows a plurality of nozzle arrays in the print head
19 of the first embodiment of this invention, with one area of the
printing element board shown enlarged. In the print head 19 of this
embodiment, the printing element board (or simply referred to as a
board) 7 is provided with a plurality of heating resistors 41 and
nozzles 49. Ink is heated by each of the heating resistors 41 to
form a bubble, whose pressure as the bubble expands is used to
eject ink from the associated ejection opening. In this embodiment,
each heating resistor is formed inside a pressure chamber and the
nozzle 49 represents a space ranging from the ejection opening to
the pressure chamber.
[0038] In the conventional printing element board such as shown in
FIG. 11, each pressure chamber 96 is provided with the ink path 97
on one side only. Because of this configuration, the pressure
generated as the bubble is formed may escape toward the ink path 97
side, with the result that the ejected ink may stray from the
intended direction, which is perpendicular to the printing element
board. To deal with this problem, in the printing element board 7
of this embodiment two ink paths are formed for each nozzle 49 and
independent ink supply ports are provided on both sides of the
nozzles 49 so that ink is made to flow into each of the nozzles 49
from both sides. In this configuration, the pressure escape during
bubble generation is symmetrical with respect to the nozzle 49 such
that the ink can be ejected perpendicular to the printing element
board 7.
[0039] Further, for the same color of ink, the printing element
board 7 of this embodiment is provided with four nozzle arrays
having a plurality of heating resistors 41 and with five ink supply
port arrays arranged on both sides of the nozzle arrays, each ink
supply port array comprising a plurality of ink supply ports.
Portions 43 in the printing element board that are situated between
adjoining ink supply ports 42 (also referred to as beams) in an ink
supply port array A (first ink supply port array), exist between a
nozzle drive circuit 44 and a nozzle array A (first nozzle array).
Similarly, beams 45 in an ink supply port array B (second ink
supply port array) exist on the nozzle array group center side of
the nozzle array A, between the nozzle array A and a nozzle array B
(second nozzle array). Further, beams 46 in an ink supply port
array C exist between ink supply ports 48 of the center ink supply
port array C.
[0040] FIG. 5 is a cross section taken along the line V-V' of FIG.
4. The beams in the printing element board between the ink supply
ports communicating with a common liquid chamber 55 that is
provided on one side of the printing element board 7 are equal in
thickness, and this thickness is taken as T. That is, the depths of
the ink supply ports are all equal to the thickness T, with ink
supplied from the common liquid chamber 55 through the ink supply
ports with a depth T to the opposite side of the printing element
board.
[0041] In this embodiment, the ink supply ports are arranged to
establish a heat resistance relationship among the beams such that
beam 43<beam 45.ltoreq.beam 46. More specifically, the
arrangement of the ink supply ports is made such that the heat
resistances of the beams in each ink supply port array, defined by
L/(W.times.T) where L is the length of the beam and W.times.T the
cross-sectional area of the beam, meet the following
relationship:
L43/(W43.times.T)<L45/(W45.times.T)L46/(W46.times.T) (Equation
1).
[0042] The heat generated by the heating resistors 41 is
transmitted through the beams and released from near the nozzle
drive circuit 44 at both sides of the nozzle array group where the
board has an increased thickness. That is, the heat is dissipated
through the printing element board from both ends of the common
liquid chamber provided at the back (when viewed from the front
side of FIG. 4) of the printing element board 7. The beam 45 in the
ink supply port array B works as a heat dissipating path for the
nozzle array B, whereas the beam 43 in the ink supply port array A
works as a heat dissipating path for both the nozzle array A and
the nozzle array B, so a greater amount of heat passes through the
beam 43 than the beam 45.
[0043] FIG. 6 shows a comparative example with respect to this
embodiment. This diagram shows enlarged a part of a printing
element board in which the ink supply ports are arranged, without
considering differences in heat flux among beams, so that a
relatively large volume of heat can pass through any of the beams.
Although this arrangement of ink supply ports 51 in such a way as
to enable any of the beams 50 to pass a relatively large volume of
heat has an advantage of improved heat dissipation, there is a
disadvantage. That is, since the width of each beam needs to be
increased, the opening dimension of the ink supply ports, in the
direction that the ink supply port array is aligned, becomes
smaller. To ensure the necessary volume of ink supply, the
dimension of the ink supply ports, in the direction perpendicular
to the direction of ink supply port array needs to be increased,
resulting in an increased size of the printing element board
itself, which is not desirable.
[0044] For this reason, the heat resistance of the path through
which a large volume of heat passes, as with the beam 43 of this
embodiment, is made relatively small to minimize the temperature
rise in the beam 43 caused by heat resistance. In that case, while
the individual ink supply ports 42 of the ink supply port array A,
in which the beams are formed, become relatively large to ensure a
predetermined volume of flow, other ink supply ports can be made
relatively small. That is, since the beams 45 through which a
relatively small amount of heat passes can be narrowed to a point
short of where the temperature rise caused by the heat resistance
begins to pose a problem, the overall size of the printing element
board 7 can be reduced while at the same time preventing an overall
temperature increase.
[0045] In this embodiment, nozzles in each nozzle array are
arranged at 600 dpi and ink supply ports at 300 dpi. The depth of
ink supply ports and the thickness of beams are approximately 100
.mu.m and almost constant throughout the nozzle array group. The
opening area of the ink supply ports 42 needs to be more than a
predetermined area (2800 .mu.m.sup.2 or more in this embodiment) in
order to meet the intended ink supply performance. If the ink
supply ports are arranged to satisfy Equation 1, and the size of
the ink supply ports 42 in the array of the beams 43 is
(length.times.width)=70 .mu.m.times.40 .mu.m, the width of the
beams W43=44.5 .mu.m. Again, if the size of the ink supply ports 47
and 48 in the array of beams 45 and 46 is 54 .mu.m.times.52 .mu.m,
the width of beams W45 and W46=32.5 .mu.m.
[0046] As described above, among ink supply port arrays formed on
both sides of each of the nozzle arrays, the heat resistance of the
portion of the printing element board 7 between the ink supply
ports (beams) is reduced in those arrays that are situated on the
end sides of the printing element board 7 (end sides of the common
liquid chamber). This has resulted in an ink jet print head being
actualized which has a reduced size of the printing element board
with a minimal temperature rise through efficient heat dissipation
and which can eject ink perpendicularly therefrom.
Alternative Implementation
[0047] FIG. 7 shows an example of an alternative implementation of
the present embodiment. While in FIG. 4 five ink supply port arrays
have been shown, the example of FIG. 7 has only three ink supply
port arrays so as to further reduce the size of the print head and
reduce costs. In this configuration, the nozzles 49 in the nozzle
array A have only one ink flow path. Hence, these nozzles 49 take
longer to refill than the nozzles that have two ink flow paths
through which ink flows into each nozzle(the nozzles of nozzle
array B), slowing the overall print speed of the print head.
[0048] However, by utilizing the present invention and arranging
the ink supply ports in ways that satisfy Equation 1 (excluding the
terms of L46 and W46), the size of the print head can be reduced
significantly while minimizing the overall temperature rise in the
print head.
[0049] If small nozzles with a small ejection volume are to be
installed to obtain high-quality images with improved granularity,
these small nozzles are positioned in the nozzle array A.
Generally, small nozzles with a small ejection volume have a
shorter refill time due to their small ejection capacity. The use
of small ink nozzles can shorten the refill time of the array A of
nozzles with only one ink flow path and therefore prevent the
overall print speed of the print head from slowing down as it would
if the normal-size nozzles were used.
[0050] As described above, in the case of the printing element
board having small nozzles with a small ejection volume and capable
of producing high-quality images, too, application of the present
invention can actualize a reduced size ink jet print head that a
minimal overall temperature increase in the printing element board
and which can eject ink perpendicularly therefrom.
Second Embodiment
[0051] Now, a second embodiment of the invention will be described
with reference to the accompanying drawings. The basic
configuration of the ink jet print head of this embodiment is
similar to the first embodiment, so explanations will be made of
only configurations particular to this embodiment.
[0052] FIG. 8 shows a group of nozzle arrays in a print head 19 of
the second embodiment of this invention, with a part of the
printing element board shown enlarged. As for the nozzle arrays of
the ink jet print head of this embodiment, left and right nozzles
are driven almost symmetrically with respect to a center line 0
during printing. Particularly during printing operations at the
high-density portions of an image, where the nozzles get
intensively heated, heat is considered dissipated toward the
outside of the nozzle arrays. Beams 70 are not in the heat
dissipation path and therefore have almost no effect on heat
release efficiency. So, as shown in FIG. 8, to further narrow the
width W70 of the beams 70, the size of ink supply ports 71 on the
center line O is set to 46 .mu.m.times.60 .mu.m and the width of
beams to W70=24.5 .mu.m. This arrangement can actualize an ink jet
print head that has a reduced size with a minimal overall
temperature rise in the printing element board and which can eject
ink perpendicularly therefrom.
Alternative Implementation
[0053] FIG. 9 shows an example of an alternative implementation of
this embodiment. The central ink supply port 80 is made a
continuous port having no beam at all in order to reduce the size
of the printing element board while at the same time meeting the
required ink supply performance. As for the beams 43 and 45, which
constitute the heat dissipation paths, the width W43 of the beam 43
is increased to meet Equation 1 of the first embodiment. This
enables the realization of an ink jet print head that has a reduced
size with a minimal overall temperature rise in the printing
element board and which can eject ink perpendicularly
therefrom.
Third Embodiment
[0054] Now a third embodiment of the invention will be described
with reference to the accompanying drawings. The basic
configuration of the ink jet print head of this embodiment is
similar to the first embodiment, so only configurations particular
to this embodiment will be explained.
[0055] FIG. 10 shows a group of nozzle arrays in a print head 19 of
the third embodiment of this invention, with a part of the printing
element board shown enlarged. To meet demands for faster printing
speed and more vivid, high-quality images, the ink jet print head
of recent years often has formed therein nozzles capable of
ejecting ink droplets of different volumes. This embodiment is an
example wherein the present invention is applied to an ink jet
print head having such nozzles with different ejection volumes. In
FIG. 10, when the nozzle array A and the nozzle array B have
different ejection volumes, the nozzles with the greater ejection
volumes are installed in the nozzle arrays A, that are closest to
the nozzle drive circuits 44 at both sides of the nozzle array
group where the board thickness increases.
[0056] In this embodiment the nozzle array A is comprised of
nozzles with a droplet ejection volume of 5-7 pl and the nozzle
array B is comprised of 1-3 pl nozzles. If ink droplets of 5 pl or
more are to be ejected from the nozzle array A, the heat resistors
90 are required to have an area of about 484 .mu.m.sup.2 or more.
If ink droplets of 3 pl or less are to be ejected from the nozzle
array B, the heat resistors 91 need to have an area of about 324
.mu.m.sup.2 or less. Since the amount of heat generated by the
nozzle array is almost proportional to the area of its heat
resistors, the nozzle array A produces a greater amount of heat
than does the nozzle array B. So, putting the nozzle arrays A,
which produce a greater amount of heat, on both sides of the nozzle
array group and reducing the heat resistance of the beams 43 is
effective for efficient heat dissipation. Further, because the
amount of heat produced by the nozzle arrays B is relatively small,
sufficient heat dissipation can occur without having to make the
heat resistance of the beams 45 and 46 as small as that of the beam
43. With this arrangement an ink jet print head has been actualized
which has a reduced size and an overall minimal temperature
increase in the printing element board and which can eject ink
perpendicularly therefrom.
[0057] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0058] This application claims the benefit of Japanese Patent
Application No. 2009-026170, filed Feb. 6, 2009, which is hereby
incorporated by reference herein in its entirety.
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